The proposed studies use a novel experimental model of viral latency and reactivation that utilizes primary memory cells as targets. Using this system, we plan to understand in detail the mechanisms that HIV-1 uses to establish latency in vivo, as well as the physiological signals that trigger viral reactivation. Knowledge from these areas will be applicable in future translational studies that will seek compounds mimicking or antagonizing the relevant signaling pathways, with the ultimate goal of destroying the latent reservoir. PUBLIC HEALTH RELEVANCE: HIV-1 in infected individuals establishes a relatively small, but long-lived reservoir of latently infected cells. Latent infection is associated with low or no viral gene expression and, accordingly, appears to be non-cytopathic. Latent viruses can undergo reactivation, giving rise to new productive infections that carry full pathogenic potential. The cell type that harbors this long-lived, latent viral reservoir is thought to consist of quiescent memory T cells. We present a novel ex-vivo model for the study HIV latency as well as its reactivation. This model faithfully recapitulates salient features of the in vivo latent reservoir. For example, latent proviruses in this system are devoid of any detectable gene expression, yet, they are perfectly competent for gene expression when reactivated by a number of external stimuli. This model uses primary, human CD4+ lymphocytes and viral integration is polyclonal. This powerful, yet straighforward experimental system will allow us to (i) assess the relative permissivenes of various CD4+ T cell subsets to harbor latent proviruses;(ii) explore signaling pathways that may preclude the establishment of latent infections and/or induce reactivation of latent proviruses;and (iii) explore the use of select agonists and antagonists of the relevant signaling pathways to experimentally manipulate latency and reactivation. Ultimately, HIV-1 eradication will require a profound understanding of the biological processes that control entry and exit from latency.